Compression distillation apparatus



June 22, 1965 F. J. NEUGEBAUER ETAL COMPRES S ION D1 STILLATIONAPPARATUS Filed Dec. 26, 1957 9 Sheets-Sheet 1 /?anz r/I/Me@ebauerfawara. a.s tena der 9 Sheets-Sheet 2 June 22, 1965 F. J. NEUGEBAUERETAL GOMPRESSION DISTILLATION APPARATUS Filed Des. 2e 1957 [dwra' 13.Aus

June 22, 1965 F. J. NEUGEBAUER ETAL 3190317 COMPRESSION DISTILLATIONAPPARATS F'i1ed Dec. 26. 1957 9 Sheets-Sheet 5 June 22, 1965 F. J.NEUGEBAUER ETAL 3190317 COMPRESSION DISTILLAI'ION APPARATUS WIPER SPL'ED0VE/P-ALL HE/97' TRANSFER COE'F/"ICIENT June 22, 1965 F. J. NEUGEBAUERETAL I COMPRESSION DISTILLATION APPARATUS 9 Sheets-Sheet 5 Filed Dec.26, 1957 June 22, 1965 F. J. NEUGEBAUER ETAL GOMPRESSION DISTILLAI'IONAPPARATUS 9 Sheets-Sheet 6 Filed Dec. 26. 1957 June 22 1965 F. J.NEUGEBAUER ETAL 3190817 COMPRESSION DIS'I'ILLATION APPARATUS 9Sheecs-Sheet 7 Filet. Das. 26, 1957 June 22, 1965 F. J. NEUGEBAUER ETAL3190817 COMPRESSION DISTILLATION APPARATS Filed Des. 26, 1957 9Sheets-Sheet 8 F. J. NEUGEBAUER ETAL 3,190817 COMPRESSION DISTILLATIONAPPARATUS Filed Des. 26, 1957 9 Sheets-Sheet 9 United States Patent O3190,817 COMPRESSION DISTILLA'IION APPARATUS Franz J. Neugehauer,Schenectady, and Edward L. Lustenadex, Scotia, N.Y., assignors toGeneral Electric Company, a corporation cf New York Filed Dec. 26, 1957,Ser. N0. 705,481 3 Claims. (Cl. 202-+236) Our present application is acontinuation-in-part of our application Serial N0. 677,628, filed August12, 1957, now abandoned, entitled Compression-Distillation Apparatus,and which is assigned t the assignee of this present application.

Our invention relates t0 compression distillation apparatus. While wecontemplate its particular uscfulness in the distillation of seawater o1brackish water to produce potable water for domestic, municipal,industrial, and agricultural uses, it has numerous other applications.For exarnple, it is useful for the evaporation and concentration 0ffruit juices, and other materials in the food industry, for removingminerals and solids from brackish, waste, o1 irradiated water, and forother purposes.

Our invention relates morc particularly to the form of such apparatus inwhich both evaporation and c-ondensation take place from oppositesurfaces of the same sheet of material, or heat conducting vaporbarrier, and in which a pressure differential, and resultant temperaturedifferential is applied across the harrier. Such distillation apparatusmay operate at pressures in the neighborhood cf atmospheric pressures orunder high vacuum, as, for exarnple, two pounds per square inchabsolute. In this latter case, they a1e enclosed in a vacum charnberwhich, in large installations, hecause of this high vacuum, is ofexpansive construction.

An object of our invention is to provide such a systern in which maximumeffectiveness; i.e., maximum production of distillate, is obtained byaccomrnodating a maximum amount -of barrier; i.e. evaporation andcondensation surface in such a vacuum chamber, thereby producing maximumutilization of the chamber.

In one form of distillation apparatus of the prior art (see HickmanPatent 2734023 issued February 7, 1956), the barrier is in the -form oflarge rotating sheet metal charnbers in which evaporation takes placefrom either the inner or outer surface and condensation takes place onthe opposite surface. These charnhers rotate at high circumferentialspeed, for exarnple 400 r.pm. at eight feet diameter, to distri-butedistilland o ver the surface by centrifugal force many times the forceof gravity.

An object -of our invention is to prcvide a system having therrnalefiectiveness approximating that obtained in systems of the type ahovereferred to and in which all heat transfer surfaces are stationary,thereby eliminating the cost and diflficulties attendant upon the use ofbearings and large rotatable components, such as problems of Balance,critical frequencies 0f rotation, etc.

Distillation systems having stationary barriers in which vaporizationtakes place on one side 0f the barrier and condensation takes place onthe other are known in the art. Certain of these constructions, fo1example the well known Kleinschmidt still, have found considerable usein applications justifying the production of distillate at high cost, ason shipboard, laut their application has been largely limited torelatively small installations. While such systems have the advantage ofconserving the heat released by condensation and utilizing it to eifectvaporization, their therrnal eifectiveness is W and, as commerciallyapplied, the structures are expensive to construct and to operate.

A further object of nur invention is to provide, in a compressiondistillation system, a more satisfactory means for distribut-ing thedistilland over the evaporation sun face in a uniform film which has nosubstantial downward gravity flow component, and which coverssubstahtially the entire evaporating surface of the barrier f0r mosteffective evaporation. At the same time, an object of our invention isto provide a system which does not have patts rotating a1: high speed,which does not rcquire precision manufacture, and which is economical toproduce and operate.

In accord with' one forrn of our invention, the evaporation surface is asimplecylinderboth the inner and outer surfaces o1": which are in vaporwhich may be either at near atmospheric pressures or at high vacuum. Theinner surfce of the cylinder is wiped by a wiper in the forrn of, andwhich operates as, a slipper bearing which rotates ab0ut the innerperiphery cf the cylinder at a relatively 10W rate, as for example, at asuitable speed within the range from ten to 0ne hundred revolutions perminute, or at a linear speed not exceeding five feet per second. Thiswiper serves to distribute the distilland over the surface in a film,the thickness of which may readily be predetermined by proper choice ofthe pressure of the wiper against the cylinder Wall, the length of thewiper circumferentially of the cylinder, the angle between thecooperating surfaces cf wiper and cylinder, and the rate of rotation ofthe wiper. The film thickness for any given Wiper and rate of rotationmay =be determined in accord With the theory and calculations of slipperbearings just as lubricant film thickness in any bearing m'ay bedetermined. T he theory and formule for such bearings are well knbwn anda1e set forth in the text book Fluid Mechanics by R. C. Binder,published by Prentice-Hall, Inc., New York, N.Y., chapter 15,Lubrication. The film thickness may be so adjusted that the distillandfilm is distributed over the inner surface of the cylinder by therotating wiper With such thickness that it just fails of completelydrying before the next Wiping by the wiper. In this viay, the entiresurface is utilized in providing vaporizatioh and, at the sarne time,the film is cf minimum thickness and offers minimum impedance to heattransfer through the cylinder.

It is desirable that the surface does not dry completely between Wipingsfor complete dryness results in high mineral concentration andsubsequently boiling point e1evation and in deposits of minerals uponthe s'urface. This reduces the etfectiveness of the surface and maynecessitate periodic cleaning. I-Iowever, it is also desirable that thefilm be of a thickness no greater than necessary to maintain the lowestresistance -to heat flow and thal: the ower required for operation ofthe wiper be maintained Within economical limits. This requires properrelationsh.ip between pressure of the wiper against the Wiped surfaceand the angle between the wiper and the Surface, all as will bedescribed hereinafter.

Our invention is not limited to cylindrical surfaces, but sheets ofmaterial of any suitable shape may be used which have high heatconductance between the s1irfaces. The material may be flexible so thatit flexes as the wiper asses over it. This flexing aids in theprevention of the formation of deposits of minerals upon the surface andin the removal of such deposits as are formed thereon.

The novel features which We believe to be characteris'tic of ourinvention are set forth with particularity in the appended claims. Ourinvention itself, however, both as t0 its organiztion and method ofoperation, together With further objects and advantages thereof, maybest be understood by reference to the following de'scription taken inconnection with the accompanying drawings, in Which FIG. 1 represents anembodiment of nur invention;

FIG. 1a illustrates one form of wiper in greaiter detail;

FIG. 1b illustrates a modification thereof;

FIG. 2 is a cross-sectiomal view showimg the distilland supply ports andcomcluits With still a third forrn of wiper for distributing thedistilland over the surface of the cylimder;

FIG. 3 is a cross-sectiomal view of the apparatus shown in FIG. 2;

FIG. 4 shows our imvemtiom im a multi-umit still;

FIG. 5 shows certaim characteristics of the equiprment useful imdeterrmimimg certaim adjustments for Optimum erformance of theapparatus;

FIG. 6 shows the effect of variatioms im wiper speed m the over-all heattramsfer coefficiemt im a particulay: apparatus;

FIGS. 7 and 8 show a modification of 0ur imvention ermbodyimg aditferemt form of wiper for the evaporating surface;

FIGS. 9 and 10 show a modificatiom of the imvemtiom im which thedistilland distribution system is combimed with the wiper mechamism formore effective distributiom 0f distilland over the evaporatimg surface;

FIG. 11 shows still a further modificatiom of the invemtion imvolvimgWipers of a further comstruction;

FIG. 12 shows the appearamce of distillate 0m the outer surfaces of thecylimder of the embodiment shown in FIG. 1;

FIGS. 13, 14, and 15 show means for more effectively removimg distillatefrom the comdemsimg surface and imcreasimg the production of comdemsate;FIGS. 16 and 17 show a form of the imventiom in which the evaporatingand comdensimg surfaces are flat rather than cylindrical and showfurther meams for more effective wiping of the evaporatimg surface;

FIG. 18 shows a forrm of the imventiom employimg flat surfaces andwipers for both the evaporating and comdensimg surfaces;

FIG. 19 shows a cutaway view in perspective of the form of the invemtiomshown im FIG. 18;

FIGS. 20 and 21 show meams for recirculatimg excess distilland, ordistilland with concemtrated mimeralization, through the still forfurther extraction of water therefrom; and

FIG. 22 shows a group of cylimders arranged together as im a multipleumit still. The particular form shown is ome in which the distilland isumder pressure and is used to drive the Wipers cf the several umits.

Referring now to FIG. 1, We have shown our imvemtion as comprisimg acylindrical housimg 1 extendimg betweem a baseplate 2 and a coverplate3, between which plates it is held by meams of rods 4. This housiug,with its end emclosures, presently to be described comprises a chamberemclosimg equipment comstructed in accord with our imvemtiom. Thischarnber may be operated at any desired pressure and temperature,includimg pressures im the meighborhood of atmospheric pressure. It mayalso, for exarnple, be evacuated to a pressure of about two pounds persquare inch absolute im any suitable way.

Within the housing 1 and coaxial therewith is a further cylimder 5 ofthim material havimg good heat comducting properties such as copper. Thebottom of cylimder 5 is spaced from the housimg by a raised portion 6 ofthe baseplate and the top is spaced from the housing by a CO1- lar 7havimg perforatioms 8 thereim for the passage of vapor. Raised portion 6is provided with seals 10, and collar 7 is provided with a seal 11 toseal the housimg agaimst the surroundimg atmosphere.

Distilland, which may be sea water, is supplied to the immer surface ofthe cyliuder 5 through a conduit 9, the end 12 of which is coaxial Withand opens into a distributor 13. This distributor 13 has radial bores 14which carry distilland from the conduit 9 and distribute it to the immersurface of the cylimder 5.

Distributor 13 is rotated about the axis of the cylinder by a motor 15through a shaft 16 comcemtric With the cylimder. The end 12 of theconduit 9 may be suitably sealed to member 20 by means not shown toprevent escape of distilland and at the same time allow rotation of thedistributor 13 about the conduit end 12.

Shaft 16 carries ome or more wipers 17, oi which two are shown. Thesewipcrs are attachcd to the shaft through radial flamges or wipercarriers 18, and said wipers bear flexibly agaimst the immer surface ofthe cylimder to spread the distilland over the surface im a thin film.That is, the distilland is supplied to the surface immediately inadvamce of the wipers and rums down the surface 0m the leading side ofthe wipers umder the imfluemce of gravity throughout the emtire lemgthof the cylinder, the excess distilland collecting at the bottom of thecylinder and being lead oft through outlet 24. The advamcing wiper,actimg in the fashion of a slipper bearing, spreads the distilland overthe surface of the cylinder in a thim film just as a film of lubricantis formed between a bearimg and jourmal, the thickmess of the film beingcomtrolled by the desigm of the wiper, its pressure 0m the cylimder, andits rate of rotation.

T0 cause evaporatiom from the immer surface of the cylimder andcomdemsatiom upom the outer surface of the cylimder, the immer surfaceis maintaimed at a lower pressure tham that at the outer surface. Thisis effected by rmeams of a cornpressor, the rotor 21 of which is drivemby a motor 21. This rotor is operated at high speed by the motor anddraws vapor from withiu the cylinder 5 upward through apertures 22 inthe distributor 13, as shown by the arrows, from which apertures vaporpasses through the compressor and thence dowmward through furtherapertures 8 im the collar 7 into the amnular space betweem cylimder 5and housimg 1. This evacuation of the immer surface of the cylimder andcompression upom the outer surface of the cylimder produces atemperature differemtial across the barrier of, for example, fivedegrees Fahrenheit.

Evaporatiom at the immer surface, of course, removes heat from thecylinder temdiug to cool the cylinder and to cause comdensatiom on theouter surface. At the same tirne, condemsation at the outer surfacereleases heat which temds to heat the immer surface and causeevaporation therefrom.

The excess distilland collected at the bottorm of the cylinder may, imsomc cases, as in the distillatiom of brackish water, for example, berecirculated through the still for further distillation. Means foreffectimg such recirculation are illustrated im FIG. 20 later to bedescribed.

The demimeralized distillate which forms 0m the outer surface of thecylimder 5 runs down the surface of the cylimder and may be withdrawmthrough the distillate outlet 25.

The wipers 17 are of suitable flexible material, metal, fiber, orplastic, which ficxes backwatdly so that the outer surface of the wipercooperates with the immer sur= face of the cylinder in the fashiom of aslipper bearimg, thereby formimg a thim distilland film of comtrollablethickness betwcem the surfaces of the wiper and the cylinder 5 just as afilm of lubricamt forms betweem the surfacves of a jourmal and abcaring. The thickmess of such a film cam be controlled accordimg to theordimary laws of bearimg operation. Accordimg to those laws, thedetermimamts of film thickness are the lemgth of the wiper surfacecircumferemtially of the cylimder, the angle between the wiper surfaceand the immer surface of the cylinder, wiper speed, and pressure of thewiper 0m the immer surface of the cylinder. All of these parameters arecomtrollable. The mechanism is so desigmed and adjusted as to thesefactors that the film of distilland is of optimum thickness for m1aximumevaporatiom from the sur facc. Of course, if the film is too thick itoifers umneces sarily l1igl1 resistamce to heat flow. If it is too thim,the film dries up too quickly after each wiping leavimg dry and, hemce,nom-utilized area im advamce of the ncxt wiper.

For optimum film thicknessi the film dries at such a rate that the filmextends frorn wiper to wiper, but only with such miuimurn thickness asto prevent drying and resulting mineral deposit on the surface. This mayhe eflected eveh though the wipers rotate at a speed hetween 10 and 100r.p.m., er at a speed not exceeding five feet per second. This isdesirable where power comsurnption is a consideration. Films as thin astwo tenthousandtns cf an inch (.0002") have readily been produced.Ordinarily the film Will be of a thicknss less than two-thousandths ofan inch (.002") when used for water distillation.

T efiect such film formation, however, the wiper must be of a materialthat is compatible With the material of the inner surface of thecylinder 5. That is, it must not be a material that contaminat-es thesurface to be wiped or reduces its Wetting properties. lt has been foundthat at least one varicty of rubber has this objectional property. Forthe same reason also, the inner surface of the cylinder should bethoroughly cleansed of all grease or other contaminants, as by sanding,to rernove any'thing likely to reduce the wetting property of thesurface. Where the cylinder is of copper, the wiper may com;irise aflexible -strip of copper or brass, but it should be so shaped er formedas to act as a slipper bearing rather than as a scraper of the surface.is, a slipper bearing operates by virtue of a converging area betweenthe journal and the stationary bearing, this converging area beingproduced by displacernent of the journal frorn its position whenunloaded due to action of the lubricant and pressures developed thereinin response to rotation of the journal under load. In this couvergingarea, high pressures are developed sufficient to carry the bearing load,which results in the formation of a lubricating film between, andseparating, the surfaces of the journal and bearing and, hence, reducingwear of the surfaces.

In our invention, the same eifect occurs. Because of the sn1all anglebetween the surface cf the wiper and that of the cylinder, whichnormally Will not exceed 15 degrees, at their areas of adjacency, aconverging region exists and high pressures are developed in thedistilland in this converging area. These pressures resist the forceapplied to the wiper and separate the wiper surface from the cylindersurface, thereby resulting in a uniform film at the trailing edge cf thewiper.

Thus, the converging angle at the areas 0f adjacency of the wiper andevaporating surface is important. Parallel surfaces of wiper andcylinder in this area of adjacency are unsatisfactory. A1: the Sametime, the Width 0f the wiper surface adjacent the cylinder in thedirection of movement must be sufiicient to develop load carryingpressures comparable to the force applied to the wiper in the convergingarea to the extent required to produce a film of desired thickness. Verynarrow wiper surfaces and sharp edges engaging the cylinder or surface011 which the film is to be formed, are to be avoided.

FIGS. 1a and 1b both show wipers which have been used With favorableresults in structures illustrated by FIG. 1. In these figures, a stripof flexible plastic 17-is covered by a layer =of cotton cloth 17". InEKG. 1a, where the plastic 17 is of rubber, the cotton cloth 17" isdirectly in contact With the surface of the cylinder 5. lt is preferred,howtever, that the material of member 17 be one that does notcontarninate the surface to be wiped by wearing through of the covering17.

Even heiter results Were had With the structure cf FIG. 1b where a layercf glass ber, or glass cloth, 17' is employed in engagement With thesurface of the cylinder begween the cotton cloth 1'7" and the surface.In this case, the mernber 17 was of a plastic known 011 the market asKel F.

These wipers 17 in FIGS. 1a and 1b are bolted to the wiper carrier 18 bymeans of bolts 18", which may de- That v 6 sirzibly extend throughelongated holes 18' in the rnember 18, as shown, to provide adjustmentof the wipers to produce desired pressure on the inner surface ofcylinder 5, thereby to adjust the thickness of the film produced.

These FIGS. 1a and 1b both show at 19 the distilland as.it flows downthe inner surface of the cylinder by gravity and as it is piled upimrnediately in advance of the wiper. From this narrow downwardlyflowing strearn immediately in front of the wiper the distilland film ofuniform thickness throughout the length of the wiper is formed on theinner surface of the cylinder following the wiper, the film being 0fsuch thickness that it has no flow component within it Which is afiectedto any appreciable extent by gravity. All flowing liquid, includingexcess distilland and tha1; to be distributed to areas frorn which it isevaporated, is confined to the stream 19 in advance of the wiper. Thus,any impairrnent of the thermal effectiveness of the evaporating surfaceby excessive flow of liquid is avoided. The surface covered by thestream 19 is very small due to the action of the moving wiper and, thus,does not substantially reduce the" effective evaporating area.

This has great advantages over a falling film, since the cylinder 5 011which the film is formed may be many feet in length, twelve forexarnple, although its diameter may be in the neighborhood of from threeto six inches. A falling film of sufficient thickness to produceeifective evaporation from lower areas would be so thick on the upperareas as substantially to impair the eflectiveness of the upper areas.In addition, the tendencies of the liquid in a falling film to channeland cover only part of the available area is cornpletely eliminated bythe nongravity alfected, aud repeatedly renewed, film produced in theOperation of ourdevice.

Our film diminishes in thickness at increasing distances frorn the wiperonly as caused by vaporization. Thus all areas cf the verticalsurface.throughout the entire length of the tube may be covefed by thefilm, which may, at any point along the length of the wiper, be of onlysuch thickness as to extend from wiper to wiper. Thus, n1aximumeifectiveness of the entire area 0f the surface in producingvaporization is obtained.

Since the wiper is flexible, it cooperates' With the inner surface ofthe cylinder even in areas of Variation therein or damage due, forexample, to handling in manufacturing 01' shipping. The cylinder itselfmay very practically be of inexpensive, light Weight construction. Atthe same um, precision manufacture is not required in the comstructionof the wiper.

FIG. 2 better portrays the rotating distributor 13 and shows the conduit9 supplying distilland, represented by the arrows 23, as it enters thedistributor and is distributed through radial bores 14 therein to theinner surface cf the cylinder 5. Bach of the bores has a slot 26downward adjacent the inner surface cf the cylinder so that distillandis delivered directly upon the inner surface of the cylinder 5 justahead of euch wiper 17 where it run s down the whole length of thecylinder in advance of the wiper and is sp1'ead by the wiper in a filmof desired controlled thickness.

This FIG. 2 shows Wipers 17 of a diiferent construction from thatpreviously described and which are adapted for the production of verythin filrns upon the surface of the cylinder 5. These wipers are bettershown in FIG. 3. They comprise an inner strip 27, which may be of brass,and an outer strip 27, which may be of stainless steel, for example.These strips are attached at one edge in any suitable manner, as byscrews 13" which extend through elongated holes 18' in strips 27 and 27into the ends of the wiper carriers 18 and extend at right anglesthereto. The elongated holes allow adjustrnent of the strips to vary thepressure of the wiper against the cylincler Wall, thereby to vary thethickness of the film produced The strips are flexed backwardly in thedirection opposite to the direction of rotation, and the outer strip 27bears against the inner surface of the cylinder 5, against which it ispressed by the somewhat stiller strip 27, through a suitable cushioningmaterial such as rubber o1 plastic 27".

It has been found that fikns formed by wipers of this type may be sothin that unless the wipers are rotated at relatively high speed, forexample 400 r.p.m., the film formed by each Wiper is likely to dry priorto the wiping by the next wiper. Where it is desired to employ suchtl1in films, it may be desirable to increase the number of wipers, as,for example, by employing three or four wipers equally distributed aboutthe immer circumference of the cylinder 5 and operating them at a lowerspeed to reduce power consumption and to avoid dry area in advance ofthe wipers. It is preferred that the speed of rotation be not greaterthan 100 r.p.m. This may be etfected by adjustment cf the wiper toproduce smaller pressure against the wall and a resulting thicker filmupon the wall. By appropriate design of the wiper, speeds as W as 10r.p.rn. may be employed.

In the forms of the invention shown in FIGS. 1-3, only a single cylinder5 is arranged Within the housing 1. In larger installations, cylinders 5may number in the hundreds, all housed within the same housing and whichmay be served either by individual compressors evacuating the ditferentcylinders, by a small number of compressors, or by a single largecompressor evacuating many cylinders. Sirnilarly, the wipers may beoperated by individual motors, or by a common motor. Any of thesematters might be determined by the economies of the installation.

FIG. 4 shows a multi-unit compression distillation apparatus comprisinga housing 1, which may be under sub-atmospheric pressure, enclosing alarge number of cylinders 5, only five of which are shown, constructedin accord with our invention. Bach cylinder has within it a rotatingshaft 16 carrying distilland distributors 13 and wipers 17 to wipe theinner surface of the cylinders, all as previously described inconnection With FIG. 1. These cylinders are supported in place byhorizontal tube sheets P1 and P2. They extend through apertures in theupper tube sheet P1, which forrns the bottom Wall of a vapor chamber V,so designated on the drawing. They rest on sheet P2, which is providedWith bearings 24' for the rotating shafts 16 and with apertures 24through which excess distilland flows from within the cylinders intogear box 50 and, thence, away through the conduit designated Concentrateon the drawing.

Vapor charnber V has an opening O in the top Wall thereof which formsthe inlet to a compressor 19' driven by a motor 20. This compressordraws Vapor from the inner surfaces of the various cylinders 5 into thevapor chamber and, thence, through the compressor and discharges itthrough passageways 30 into the spaces between the outer surfaces of thevarious cylindrical vapor barriers 5. Here the vapor condenses due tothe cooling resulting frorn vaporization inside the cylinders, andcomdensate runs down the outer surface of the cylindrlcal vapor barriers5 onto the plate P2 and, thence, outward through the distillate outputconduit designated by the legend Distillate 011 the drawing.

The shafts 16 preferably may be hollow and each of thern extend downwardthrough the gear box 50 to a reservoir R, to which distilland issupplied under pressure from a conduit bearing the legend Distilland.From this reservoir R, the distilland is forced upward through hollowshafts 16 to distributors 13 at the upper end of the shafts whichdistribute it to the cylinders 5 just in advance of the wipers, aspreviously described.

In the gear box the shafts are provided with gears 49, which are drivenin any suitable way, as through bevel gears 48, frorn a cornmon shaft47, which may be motor operated, thereby to rotate the shafts 16 andwipers 17 at a suitable speed.

This apparatus has many advantages. Many cylinders 5 may be accommodatedin a given enclosure, thereby producing in extremely large ratio betweenarea of Vapor and condensate producing surfaces and the volurne of theenclosure. The cylinders may be small, as, for example, of the order ofsix inches 01' less in diameter, and they may be closely spacedtogether. They are shown broken away at L to indicate length. They maybe 10 or 12 feet in length. The various wiper carrying shafts may begeared together without mechanical difficulty. A single compressorscrves adequately for many cylinders.

The apparatus once constructed is capable cf operation for long periodssubstantially unattended. In large installations, such as those forsupplying water for municipalities, equiprnent of this character makespossible large Ieductions in the cost of the building for housing theequiprnent, cost of plumbing, and cost of labor for operation andmaintenance. This is of extreme importance in reducing the cost of thedistillate.

FIG. 5 shows three interrelated groups of curves A, B, and C useful incalculating certain adjustments with the objective to optimize formaximum effectiveness of the apparatus.

The curves of group A show the relationship between the utilizedfraction of the heat transfer arca of the barrier plotted as ordinateand the product of the number of wipers and the number of rotations ofthe wipers per minute plotted as a arameter. Bach curve of the group Acorresponds to a differcnt product of number of wipers times speed ofthe Wipers in revolutions per minute.

The curves of group B each correspond to a difierent temperaturediiferential across the barrier plus any distilland or distillate filmthereon.

The solid curves of group C show the relation between the sum of thecondensing film and Wall resistances to the maximum obtainable over-allheat transfer coeflficient. The dashed curves of group C indicate therequired film thickness directly behind the wiper.

From these curves, assembled as illustrated in FIG. 5, the relationshipbetween the important design and operating arameters can be read. Thedotted lines and arrows show the procedure which may be followedAssuming, for exarnple, that a given percentage of the area of thebarrii-Ir is covered with evaporating film, the remaining portion beingblocked by the wiper itself, and distilland running down the surface inadvance of the wipe; a line D may be drawn horizontally to the curvegroup A corresponding to the product of the numbe1 of wipers used andthe speed of rotation of the wipers. Thence, a line E may be drawndownward to that curve of the group B which corresponds to thetemperature differential across the vapor barrier plus the filmsthereon. Thence, the line F may be drawn horizontally until itintersects with the solid curve of the group C which corresponds to theparticular sum of the comdensing film and wall resistance to heattransfer. The required film thickness directly behind the wiper may beread at this point from the dashed curves of group C. From this point, aline G may be drawn upward vertically to the scale H, designated on thedrawing as Owr-all Heat Transfer Coefficient related to utilized surfacearea.

In a sirnilar way, a curve may be predicted such as that shown in full1ines in FIG. 6. This curve shows the relation between wiper speedplotted as abscissa and the over-all heat transfer coeffieient asordinate for otherwise constant operating conditions. By varying thewiper speed and determining the over-all heat transfer coefficient asabove described, an optimum point appears in the curve. This point isdesignated by the legend Optimum. At this point, the rate of rotation ofthe wiper is just auch that the film extends from wiper to wiper. lt hasbeen found preferable, however, to assure wetness of all partg cf thesurface With a reasonable margin of safety und in order to preventdeposit of minerals upon the surface to operate the wipers at a slightlyhigher speed; for example, at a speed corresponding to the pointindicated by an X on the curve.

The dash line curve and points indicated by small circles in FIG. 6represent actual experimentally determined results. The diiferencebetween the predicted cu rves and the test points at very 10W wiperr.p.m. is cxplained by the presence of superirnposed falling film, notconsidered in the theory, and the eifect f which is negligible at normaloperating r.p.m. T he left extremity of the dash line curve representsthe over-all heat transfer coefficient for zero wiper speed; i.e., acondition in which the film is entirely a gravity falling film, It Willbe seen that this coeificient is far less favorable than thoserepresented by the portions of the curve to the right cf the optirnumpoint.

FIG. 7 shows wipers 27 of a still diiferent forrn. This wiper comprisesa lever 28 pivoted at an intermediate point 29 to a rotating arm 32 onthe shaft 16. The shaft 16 rotates in the direction inciicated by thearrow so as to carry the Wipers 27 about the inner surface of thecylinder against which it hears by reason of centrifugal force todistribute distilland in a thinfilm over such surface. es stainlesssteel, brass, or copper, or of carbon, or like material.

The external surface 33 of the wiper 27 is designed t0 cooperate withthe inner surface 0f the cylincler 5 in the fashion of a slipper bearingto forma a film between it and the cylinder of a thickness controlled bythe applied pressure, or bearing load, the length L cf the wiper, thewiper wedge angle 0c, and the wiper speed to produce maximurnevaporation from the immer surface of the cylinder. The angle o: isshown 0n the drawing for purposes of illustration only. In practice itmay be either greater or srnaller than that illustrated. The appliedpressure may be adjusted by changing the position cf a counterweight 34along the length cf the lever 28 opposite the wiper 27 from the pivot29. The osition of the counterweight may be secured by use of a setscrew 35.

FIG. 8 shows a pl-urality of such wipers 27 arranged axially along thelength of the cylinder in end to end relation to wipe diiTerentportiomrespectively of the inner surface of the cylinder. In this way,the wiper follows more effectively all portions of the cylinder even ifthe cylinder exhibits manufacturing irregularities. All of thern arerotated together to serve as a single wiper having somewhat greateraccomrnodation to irregularities in the surface.

FIG. 9 shows an assernbly similar to that of FIGS. 7 and 8, but in whichdistilland is supplied through the shaft 16 to the arm 32, both of whichmay be hollow, from which it is released through an aperture 38 in theends of the arm 32 onto the inner slirface of the cylinder and inadvance of the wiper.

FIG. shows an arm 32 extending downward inside of the cylinder andadjacent to the inner periphery thereof and having apertures 38distributed along the length thereof t0 distribute distilland to allparts of the length of the cylinder. This reduces the volume of fluid inthe falling stream in advance of the Wiper while, at the same time,assuring an adequate supply of distilland at the lower extremities ofthe wiper.

FIG. 11 shows a flexible cylinder 5 which is distorted by wipers 46,which may be of any suitable forrn, producing sufficient pressureagainst the cylinder to eflect the distortion. They are shown in theform cf sl-ender blades extending from the axis of the cylinder andhaving rurved ends 45 bearing against the inner surface and cooperatingtherewith as a slipper bearing, but with sufi'icient force to producesome deflection or deformation of the cylinder to reduce formation ofmineral deposits thereon, 0r to release such deposits therefroin.

Of course, such a cylinder, flexed by the wipers, may be used in any ofthe forms of the invention thus far described.

FIG. 12 shows the appearance of the outer surface cf the cylinder 5during the distillation operation if drop- These wipers 27 may be of asuitable metal, such elevated position.

19 wise condensation is applied. It will be noticed that on the upperportion.of the surface large drops indicated at 51 of distillate appear,whereas farther'down the surface is shown wi th only smaller dropsclinging thereto. It has been observ&zd in the operation of theapparatus that the idistillate forms in drops which tend to cling to thesurface until they becorne of sufficient size, as, for example, ancighth of an inch in diameter, to break loose from the cylinder underthe elfect of gravity and run down the surface. In doing so, they washoft many other drops, both lange and small, clinging below and thusreleasing such drops over a very considerable area of the surface below.This goes on continuously and accounts for the fact that fewer suchdrops appea1 in the drawing below the upper region thereon.

The dwelling of large drops of distillate on the cylinder Wall isobjectionable because' they increase'- resistance to heat flow frorn thevapor to the cylinder. By their breaking loose and running down and thusclearing the area below cf such droplets, the heat flow resistance ofthe cleared area is described and the area is rendered more effective inproducing condensation. The eifectiveness of the area still fartherdown, however, is again reduced by the accurnulating film of distillate.

For maximum effectiveness of the condensing surface, it is desired thatcondensation forrn in individual droplets which drop olf while smallinstead cf clinging to the surface until they become large. This actionmay be promoted by treating the surface With certain chernicals, such asoleic acid, mercaptan, 0r silicon wax. However, such material washes 01Tafter sh-ort periods of use. The best permanent surface for dropwisecondensation is polished chrornium, but even with this surface a largearea is always covered with large standing droplets which seriouslyreduce the heat transfer desired for maximum condensation.

In accord with our invention, means 'are provided me chanically todisturb the clinging droplets in the upper portion of the cylinder tocause thern to run down the surface and thus disturb the lower dropletsand free the region ofcondensation. One means to effect this releasingof the droplets is shown in FIG. 13 which comprises a pair of permanentmagnets 54 and 55 arranged in magnetically attracting relationshipthrough' the cylinder Wall, magnet 54 being on the outside and magnet 55being on the inside of the cylinder. The magnet 55 is rotated around theinner surface of the cylinder by rotation cf the shaft 16 to which it isconnected by arm 60. In such rotation, it carries With it the magnet 54,which may be provided with a bearing surftce 56 of polyethylene, orother nonwetting materiaL such, for exarnple, a material known on themarket by the trade narne Teflon, 0r other similar material, betw-een itand cylinder. This material tends to make the sur-face nonwetting bycovering it With a molecular layer of the material itself. In itsrotation about the circumference 015 the cylinder, the magnet 54disturbs any droplets forrned about that portion of the cylinder andcauses thern to run down the outer surface 0f the cylinder to f1ee thecylinder of clinging droplets. The cylinder may be provided With ashelf-like projection 57 below the magnet to support the magnet in itsThis shelf-like projection may be provided with ape1tures 58, as bettershown in FIG. 14, through which the distillatedrops to the lowersurfaces of the cylinder.

FIG 14 is a sectional view on line 14-14 of FIG. 13.

FIG. 15 shows four such assemblies, 5460, arranged about the cylinderand spaced apart along the length thereof for better rernoval cfcondensate from the surface. It also shows at 62 such condensate as it1'UI1S down the surface of the cylinder. If desired, each cf theseassemblies, other than the top assembly, may be provided with ade-flector 63 above it to carry the distillate running down from aboveoutward away from the cylinder so 1 l that it may drop to the bottomWithut interfering with operation of the lower assembly.

By use bf several such assemblies spaced along the length of thecylinder, maximum heat transfer may be achieved.

FIG. 16 shows a form of our invention in which pressure external to theeondensing surface may aid or add to the bearing load between the wiperand the evaporation surface. In this form cf our invention, thecondensation surfaces are indicated at 72 and are shown as the flatbroad side surfaces of hollow disks 73 and 74 arranged axially to ashaft 75 concentric with the disks. These surfaces 72 of the disks arejoined together at their outer peripheries, as shown at 76, and at theirinner peripheries, as shown at 77, to form a eontinuous hollowenclosure.

At the right cf the right band disk 74 is shown a compressor 78 whichmay be driven, through gears 42, by a suitable motor to evacuate thespace within the several disks and to direct vapor produced therein intothe outer space between the disks and the unter housing 79. The shaft 75may be provided With Ieduction gears 82, the smaller one of which isdriven by a motor to produce relatively slow rotation of the shaft.

The shaft 75 is provided with Wipers S3, one, 0r any desired greaternumber, in each disk, each wiper extending radially frorn the shaft towipe the inner surface of the disks. Distilland is carried to thesesurfaces through the bore 84 in the hollow shaft and through passages 85in the wiper itself.

The form of this wiper is illustrated in FIG. 17, Which shows a sectionacross one of the wipers. The wiper may be of suitable metal or plasticcompatible with the inner surface of the disks 73 and 74, and may becurved backward to wipe the surfaces in slipper bearing fashion. Thewiper has a passage 85 extending axially of its length and lateralpassages 86 to carry distilland to the evaporating surface and todischarge it at points 87, as shown in FIG. 17, just in advance of thearea where the wiper contacts the evaporating surfaee. Any excessdistilland within the disks, such as that shown at 88, may be drained01T through conduits 89. Distillate which forms on the outer surface 72of the disk collects in the bottom of housing 79 and may be drawn offthrough a conduit 93.

OWing to the faet that the surfaces 72 are broad, flat, and to someextent flexible, pressure on the outside and evacuation on the insidecause them to flex somewhat inwardly, thus providing any additional loadneeded for film control.

FIGS. 18 and 19 show a further form of the invention in which both theevaporating surface and the condensing surface a1e wiped by wipers. Inthis case, distilland is supplied through eonduits 102 and 103 to spraynozzles 104 arranged to spray the flat rectangular parallel surfaces 105of sheet material. This sheet material is successively bent back uponitself to form, as shown in both figures, six parallel pl-anes 107, 108,109, 1 10, 111, and 112. The end portions may be brought together at thetop to form a top surface 113 above the nozzles. The edgewise surfacesmay be sealed, as shown at 114 in FIG. 19, to form a completely enclosedspace between the surfaces 105 enelosing the spray nozzles fordistributing liquid distilland over these surfaces. A compressor 116,shown in FIG. 18 but omitted from FIG. 19, is arranged between the topsurface of the enclosure 115 and the top surfaee 113 of the sheet, thelatter of which has an aperture 117 to which the compressor is connectedand through which it draws vapor from the evaporating surfaces 105 tothe pressurized space outside.

Extending at right angles to all 0f the surfaces 105 is a drive shaft118 rotated by a motor 119 carrying wipers 122 which wipe both theevaporating surfaces 105 and the opposiug condensation surfaces 124.These rnembers 122 may be blades, or wiper carriers, having mountedthereon wipers of any suitable type, such as those 12 shown in FIGS. 1a,1b, or FIG. 3, although the wipers for the condensation surfaces may besimple flat blades.

Thus, distilland enters through the conduits 102 and 103 and is .sprayedby the nozzles 104 upon the evaporating surfaces where it is distributedin a thin film by means of wipers 122 over so much of the rectangularsurface as is wiped by the rotating Wipers 122. Any excess distillandmay be lead off through conduits 125.

Vapor formed upon the surfaces 105 is carried outward through anaperture 117 by the compressor 116 through the spaee defined by thecondensing surfaces 124 and the immer surface of the housing. Thesesurfaces 124 having been cooled by evaporation from the surfaces 105,produce condensation of the vapor. The resulting distillate collectingin the bottom of the enclosure is shown at 132 and lead oft through aconduit 133.

This form of the invention has the advantage that both the evaporatingsurfaces and the condensation surfaces are wiped by the wipers toproduce a thin film of distilland and to remove the distillate, therebyto eflect maximum heat transfer through the surfaces producingevaporation and condensation.

FIG. 20 refers again to the form of invention shown in FIG. 1 but inwhich excess distilland collecting at the bottorn of the cylinder 5 isdrawn off through a conduit 135 to the input eonduit 136 where it joinsthe fresh distilland and is pumped through pump 137 to nozzles 138 andis thus recireulated over the inner surface of the cylinder 5 in advanceof the wipers 17.

In FIG. 21, excess distilland collecting at the bottom of the eylinder 5is pumped upward by gear pump 140 through the shaft 16 of the wiper,wh-ich may be hollow, to the spray nozzles 138 above the wipers. Ifdesired, fresh distilland may be pumped in the same way and may beadmitted through the hollow shaft 16 of the larger gear142 of the pump.

FIG. 22 shows a number of cylinders 5 Which may bfi arranged in closeproximity t0 each other in a single housing, not shown, and may beevacuated by a single eompressor, not shown, into the space within suchhousing. This structure may be utilized in equipment 0f the characterillustrated in FIG. 4. Each cylinder may have at its top a distributor138 fed With distilland through a hollow shaft 16 which carries thewiper carrier 18, on which may be mounted suitable wipers, not shown,and which rotates the nozzle distributor. These shafts 16 may beprovided with gears 139 at their lower ends which intermesh and whichmay serve as a fluid motor for driving the Wipers where the dist=illandis under pressure, Thus, distilland under pressure may be suppliedthrough a conduit 142 to conduits 143 and 144 leading -to those spacesabout the gears where pressure tends to cause rotation of the gears inthe desired direction. Other areas on the downstream side of the gears,as the areas 44, may be connected through suitable conduits to thehollow shaft 16, thereby -t0 supply distilland upward through the shaft16 to the distributor 138.

Of course, in situations where the distilland supply is not underadequate pressure, the various gears may be driven by an electric motor,as explained in connection With FIG. 4, and serve as pumps to pumpdistilland through the respective shafts 16 to the distributors 133, asshown in FIG. 21.

While we have shown particular embodiments of our invention, it Will, ofcourse, be understood that we do not Wish to be limited thereto sineemany modifications may be made in the structural arrangements shown andthe instrumentalities employed. We contemplate by the app inded claimsto cover any such modifications as fall within the true spirit and scopeof our invention.

What we cl-aim as new and desire to secure by Letters Patent of theUnited States is:

=1. In a still, a stationary heat exchanger and hase separation barrierforming an evaporation ch'amber 0n one side and another chamber on theother side, said 153 barrier comprising a vertically arranged cylinder fthermally conductive material forming on one of its sides an evaporatingsurface in heat transfer relationship with the opposite side of thebarrler, rneans for continuously applying distilland to saidevapor-ating surface, rotary means for spreading and flowlng saiddistilland in a thin substantially stati-onary film 011 said evaporatingsurface, rneans dncluding a pump f0r withdrawing from said evaporatingchamber vapor evolved from said film of distilland and directing suchvapor after discharge from said pump into intimate -c-ontact =W-ith theopposite side 0f said barrier for heating the same so as to transferheat tc said film on said evaporating surface to effeet the evolubion ofv-ap-or therefrom.

2. The still of claim 1 in which the evaporating surface s the innersurface of the cylinder.

3. The still of claim 2 in which the rotary means eomprises a.t leasttwo wipers extending substan1zially the full length -of said cylinderalong its vertical axis 011 opposi-te sides -thereof, said wipers slowlywiping said inner surface peniodically to distribute distilland in aIhin film -over said inner surface, the thickness of the film relativeto the interval between Wipings being such Ihat the film completelyevaporates in a period substantially equal to the period betweenwipings.

4. The cornbination in a compression distill'ation apparatus cf astationary heat exchanger and ph ase separation barrier forming anevaporation chamber on one side and another chamber on the other side,said barrier comprising a thin vertically arnanged cylinder of thermallycouductive material forming on one of its sides an evaporating surfacein heat transfer relationship with the opposite side cf the barrier,wiper means comprising a plurality of Wipers bearing against saidsurfiace and means to actuate each wiper to wipe a portion of saidsurface recurrently in the sarne direction, means to supply distillandt0 such surface in advance of the wiper in suflioient quantity to Tundown by gravity in astream concentrated against the leading edge of thewiper throughout the 1ength of the wiper With excess thereof, each wiper=haviug a bearing surface forrned to cooperate with the surface cf saidbarrier in slipper bearing fashion to produce from said stream asubsbantially stationary film of distilland between said cooperatingsurfaces due to movement of the Wipe1, said film being so thin that itevaporates in an interval approximating the lnterval prior to the nextWiping thereby to produce increased evaporation from, and cooling of,said barrier, me ans to communicate vapor from said surface to theopposite surface of said barrier, and means operating to maintain saidevaporating surface under lower pressure than said opposite surface tomaintain a temperature difierential across said barrier.

5. The combination of claim 4 in which the evaporating surface is theinner surface of the cylinder and said wipers are formed of a plunalityof sections in end to end relation along the dnner surface of thecylinder, each section being independently mounted to bear against saidsurface to accommodate irregularities therein.

6. The combination of claim 5 which includes means findependently toadjust the pressure developed between each section cf said wipers andsaid surface.

7. A compression distillation apparatus cornprising a ehamber, avertical heat conducting cylinder supported Within said chamber,said'cylinder having a length at least several times its diameter, aWiper within the cylinder extending axially thereof, means to rotatesaid wiper about the axis of the cylinder and t0 distribute distillandto the upper portion of the inner surface of the cylinder just inadvance of the wiper whereby distilland flows down the surface in astream adjacent 1:0 and preceding the mper, means to bear said wiperresiliently against said 1rmer surface at an angle forrning a convergingarea between the wiper and the surface Within which said stream flowsdownward along the surface and from which distllland is distributed bythe wiper in a uniform substantrally stationary film along the trailingedge of the wiper so thin that it is not affected by gravity andsubstantially completely evaporates before the next wdping of thesurface by the wiper, means including a pump for Withdrawmg from saidcylinder vapor evolved from the distilland therein and for directingsuch vapor With increased pressure into contact With the outer surfaceof said cylinder for heating the saure so as to transfer heat to thestationary film of distilland within said cylinder to vaporize the Same.

8. The combination, cf a flexible stationary vertically arrangedcyl=indrical barrier of heat conducting material, means to supplydistilland to the rmer surfiace of said barner for evaporation thereby,a wiper arranged fo1 rotatlon about the axis of said cylinder and tobear against sa1d inner surface to distribute said distilland in |a thinsubstantially stationary film over said surface and to distort saidbarrier thereby to reduce deposit of minerals frorn said distilland onsaid cylinder and to assist removal of such deposits therefrom, andmeans to supply vapor from said immer surface With increased pressure tosaid outer surface for condensation therebn, said means niaintaining atemperature and pressure differential across said barrier.

References Citeel by the Examiner UNITED STATES PATENTS 1501515 7/24Testrup 15924 1966938 7/34 Stone 20285 X 2,259,024 10/41 Clevelani2469729 5 49 Hunter. 2500900 3/50 Madlen 202205 2,542269 2/51 Zahm..2546380 3/51 Zahm. 2546381 3/51 Zahm. 2,764,434 9/56 Nerheim 202153 X2,766193 10/56 Schneider 202153 2793,174 5/57 Smith 202-205 2793988 5/57Latham et al 202 X 2818373 12/57 Ockrent 202-205 2,848388 8/58 Bueche202-236 X NORMAN YUDKOFF, Primary Examiner.

GEORGE D. MITCHELL, RICHARD D. NEVIUS,

Examiners.

1. IN A STILL, A STATIONARY HEAT EXCHANGER AND PHASE SEPARATION BARRIERFORMING AN EVAPORATION CHAMBER, ON ONE SIDE AND ANOTHER CHAMBER ON THEOTHER SIDE, SAID BARRIER COMPRISING A VERTICALLY ARRANGED CYLINDER OFTHERMALLY CONDUCTIVE MATERIAL FORMING ON ONE OF ITS SIDES AN EVAPORATINGSURFACE IN HEAT TRANSFER RELATIONSHIP WITH THE OPPOSITE SIDE OF THEBARRIER, MEANS FOR CONTINUOUSLY APPLYING DISTILLAND TO SAID EVAPORATINGSURFACE, ROTARY MEANS FOR SPREADING AND FLOWING SAID DISTILLED IN A THINSUBSTANTIALLY STATIONARY FILM ON SAID EVAPORATING SURFACE, MEANSINCLUDING A PUMP FOR WITHDRAWING FROM SAID EVAPORATING CHAMBER VAPOREVOLVED FROM SAID FILM OF DISTILLED AND DIRECTING SUCH VAPOR AFTERDISCHARGE FROM SAID PUMP INTO INTIMATE CONTACT WITH THE OPPOSITE SIDE OFSAID BARRIER FOR HEATING THE SAME SO AS TO TRANSFER HEAT TO SAID FILM ONSAID EVAPORATING SURFACE TO EFFECT THE EVOLUTION OF VAPOR THEREFROM.